The specific aim of the proposed research is to identify and examine age-related and mediating factors that influence HIV risk among illicit, injecting drug-users (IDUs) not-in-treatment who are 50 years of age or older. A social network perspective guides the project's sampling procedures and overall research design and analysis. The effects of age and cohort-related influences (such as biological aging, social network affiliations, and life course circumstances) in conjunction with mediating factors (such as gender, method of procurement of drugs, perception of risk) on high-risk drug-use and sexual behavior will be examined. A total sample of 50 high-risk, active injectors not in- treatment who are 50 years of age or older will be drawn from a pool of IDUs enrolled in a community-based HIV counseling, testing and partner notification project. Three data collection sources will provide information and measures for the analysis: First, a focus group session of 10 participants will be used to explore and collect group level information about age and cohort-related factors that condition HIV risk among older IDUs. Second, 40 older injectors will be interviewed in- depth about their drug-use, HIV risk behavior, social network relationships, health status, and the biological, social, and contextual factors that shape their actions. Third, secondary data analysis of self-reported risk-behavior by the 40 older injectors obtained by the community-based project prior to HIV testing will provide additional information on high-risk practices. The resulting information will be used to develop an age-appropriate, HIV-prevention model for older injectors that can be implemented and tested at multiple sites under the RO1 funding mechanism.